Milky Way-Andromeda Collision Now Less Certain

Milky Way-Andromeda Collision Now Less Certain

Why in the News?

A new study published in Nature Astronomy suggests that the long-feared collision between the Milky Way and Andromeda galaxies may not be inevitable. Updated data show a 50-50 chance of such an event within the next 10 billion years. This revelation has sparked interest in understanding more about our galactic neighborhood and the question of how many galaxies are there in the observable universe. The study also highlights the importance of galaxy images and astronomical observations in predicting future scenarios for these big galaxies.

Background and Scientific Basis:

• The Andromeda Galaxy, also known as galaxy M31, located 2.5 million light-years from Earth, is moving towards the Milky Way galaxy at 110 km/s. It is considered the nearest galaxy to the Milky Way and the biggest galaxy in our Local Group. Many wonder if we can see the Andromeda galaxy from Earth, and indeed, it is visible to the naked eye under dark sky conditions.
• Earlier predictions indicated a high merger probability within 5 billion years, potentially forming a new elliptical galaxy called Milkomeda.
• New simulations, based on observations from Hubble and the Gaia space telescope, suggest that the Andromeda and Milky Way collision is no longer certain. These simulations take into account factors such as dynamical friction and the proper motion of galaxies.
• Gravitational influences from nearby galaxies like Triangulum (also known as M33) and the Large Magellanic Cloud have altered previous forecasts. The M33 gravitational pull, in particular, plays a significant role in these calculations, affecting the orbital trajectory of both the Milky Way and Andromeda.

New Findings and Impact

• The updated model gives a 50% merger probability in the next 10 billion years, based on new astronomical measurements and astrophysical simulations. This merger probability is significantly lower than previously thought.
• Triangulum’s (M33) gravitational pull increases the chances of a merger, while the Large Magellanic Cloud’s influence reduces it. The interplay between these galaxies near the Milky Way complicates predictions.
• A head-on collision could reshape the Milky Way from a spiral galaxy into a stellar blob, fundamentally altering the Milky Way galaxy facts as we know them. This potential Milkomeda galaxy would be a result of complex galaxy evolution processes influenced by dynamical friction.
• Alternatively, a near-miss flyby may leave the real Milky Way galaxy largely undisturbed. The outcome depends on various factors, including the transverse velocity, galaxy masses, and dark matter distribution of both the Milky Way and Andromeda.

Long-Term Relevance and Uncertainty

• The sun’s life cycle will end in ~5 billion years, long before any potential cosmic collision between these spiral galaxies. This timeline is crucial for understanding the Earth in Milky Way galaxy context.
• Earth, which is located in the Milky Way galaxy, may be engulfed or scorched by the expanding sun, rendering collision outcomes irrelevant for humanity.
• Researchers highlight that more accurate data on galaxy positions, masses, and proper motion are needed to refine predictions of galactic orbits and celestial mechanics. The role of dark matter in these interactions is also a subject of ongoing study within the Local Group.
• Astronomer Sawala adds a grim note: humanity may end itself far earlier, without cosmic help from any galactic merger.